The Presence of a Motility Inhibitor Within Spermatozoa May Explain the Poor Sperm Motility of Some Infertile Men

The presence of motility inhibitors in seminal plasma and within spermatozoa from control and infertile men with poor sperm motility was investigated using demembranated reactivated human spermatozoa. No difference was found in the inhibitory capacities in seminal plasma of patients with poor sperm motility (less than 50%) when compared with that of fertile controls with motility above 50%. No correlation was observed between inhibitory capacity and sperm motility. However, when extracts of spermatozoa from these patients were tested for the presence of inhibitor, it was observed that three of nine patients had an inhibitor in their sperm extract. By contrast, all sperm extracts from fertile control subjects were devoid of inhibitor. It was concluded that the presence of a motility inhibitor in seminal plasma does not explain the poor sperm motility observed in patients. The presence of a motility inhibitor within spermatozoa, however, may represent an important factor in the etiology of the poor sperm motility observed in some patients.